A conveying apparatus provided with means for vacuum adhesion is used for executing an operation to handle, for example, a work material, that is, an operation to pick up the work material placed at a standby position, and to convey the same to a predetermined position to be unloaded at the predetermined position.
With such a conveying apparatus provided with means for vacuum adhesion, the material adhered can be easily released by the agency of gravity simply by applying vacuum break thereto upon reaching the predetermined position unless material conveyed is sticky, or extremely light in weight. However, in the case of conveying by means of vacuum adhesion an intermediate process material used in manufacturing, for example, tires, particularly, a sticky material such as plies, belt, and so forth, it is not easy to separate the material already adhered from a vacuum face of the conveying apparatus. That is, simply by feeding break air to a vacuum duct, and so forth, separation cannot be completed, resulting in incomplete separation at times. If the separation is incomplete, a portion of the material remains adhered in a state as-adhered to the vacuum face of the conveying apparatus when the vacuum conveying apparatus is in return operation after conveyance of the material, causing problems such as entrainment, and so forth, of the material due to inertia of the material that has been transferred at a high speed (3 m/sec), causing deviation in position. For this reason, means for facilitating separation have since been desired.
To cite an example although not in any Patent Document, in order to enhance separation property of a vacuum face of a vacuum conveying apparatus, surface treatment such as Teflon (registered trademark) coating is applied to the vacuum face, and the vacuum face is provided with a plurality of nozzles for jetting air to the suction-adhered material as supplementary means for promoting separation of the material, together with a multitude of vacuum adhesion orifices communicating with vacuum piping and vacuum ducts, thereby mitigating the adhesion force due to stickiness of a sticky material by the effect of the surface treatment when releasing the sticky material adhered, and forcefully separating the sticky material adhered by jetting air thereto.
With the conventional vacuum conveying apparatus, however, because time a delay occurs before the sticky material is released from vacuum adhesion even if break air is sent into the vacuum piping and so forth when the sticky material has been conveyed to a predetermined position, it is not possible in practice to immediately and completely separate the sticky material as adhered off the vacuum face even by jetting air thereto. Accordingly, the actual situation is that thr vacuum force is adjusted according to a degree of stickiness of material to be conveyed, and the shape thereof, so as not to allow a vacuum force greater than necessary to act thereon. Further, it is difficult to implement satisfactory coating of the vacuum face by the Teflon (registered trademark) coating, and so forth, so that satisfactory separation property is not necessarily provided.
Thus, with the conventional vacuum conveying apparatus, because of poor separation response of the vacuum break at the time of release, delay time is required between actuation of release by the vacuum conveying apparatus, and actual proceeding to the following step of operation, so that operation time is increased, thereby reducing productivity.
Further, with the conventional vacuum conveying apparatus, if the material to be adhered moves in a slightly zigzag direction, that is, is out of a normal position, an end of the material deviates from a region of the vacuum adhesion orifices of the vacuum face, and the atmosphere flows into the vacuum duct through part of the vacuum adhesion orifices, so that the suction pressure of the vacuum duct drops, thereby failing to perform normal adhesion. With the conventional vacuum conveying apparatus, this necessitates countermeasures to raise the suction pressure of the vacuum duct, and so forth, in addition to installation of an expensive device for preventing zigzag moves; however, if the suction pressure is raised, this will result in improper release of the material, as described above.
Further, with a conventional structure in which the vacuum face is caused to move up and down exactly according to up and down moves of a piston of an air cylinder, for example, in the case where the vacuum conveying apparatus standing by on a conveyer is caused to come down once to pick up the material to be adhered, and to immediately make an upward move, the piston is caused to rise after it has fully reached a bottom dead center, so that delay occurs at the bottom dead center. Accordingly, if the operation is executed at an estimated timing in order to avoid such delay, this will cause a problem that the piston rises before reaching the bottom dead center, thereby inducing improper adhesion.
The invention has been developed to solve such problems as encountered in the past, and it is therefore a first object of the invention to speedily implement a release operation of suction-adhered material by enabling the material, even if it is sticky, to be released immediately and with reliability at a release position.
A second object of the invention is to hold material as adhered with reliability, and without particular need for raising vacuum force even if the material as adhered moves in a slightly zigzag direction.
Further, a third object of the invention is to enable high-speed operations for adhesion, conveyance, and separation, respectively, to be implemented by reducing time delay occurring during up and down moves of a vacuum face.